The late Pliocene–Pleistocene paleoenvironment has been reconstructed based on three-dimensional seismic data from the southwestern Barents Sea continental margin. During the late Pliocene–early Pleistocene, continental slope sediments were predominantly deposited from meltwater overflows and underflows. The seismic stratigraphy of the early–middle Pleistocene shows both glaciomarine sediment input from channelized meltwater discharge and the first indications of large debris-flow deposits on the continental slope, originating from input of subglacial deformation till eroded and transported by ice streams. During the middle–late Pleistocene, large debris flows dominated the slope succession. From the above results we infer the following evolution in the Barents Sea: (1) a temperate Barents Sea Ice Sheet with channelized meltwater flow developed during the late Pliocene–early Pleistocene; (2) alternating glacial periods of ice with channelized meltwater flow and the first periods of ice, including ice streams, characterized the early and middle Pleistocene; and (3) more polar ice conditions and a Barents Sea Ice Sheet that mainly included large ice streams, with little or no channelized meltwater flow, occurred in the middle and late Pleistocene.